Sulfur
Sulfur is pale yellow, odorless, brittle solid, which is insoluble in water but soluble in carbon disulfide. In every state, whether gas, liquid or solid, elemental sulfur occurs in more than one allotropic form or modification; these present a confusing multitude of forms whose relations are not yet fully understood.
In 1975, University of Pennsylvania scientists reported synthesis of polymeric sulfur nitride, which has the properties of a metal, although it contains no metal atoms. The material has unusual optical and electrical properties.
High-purity sulfur is commercially available in purities of 99.999+%.
Amorphous or "plastic" sulfur is obtained by fast cooling of the crystalline form. X-ray studies indicate that amorphous sulfur may have a helical structure with eight atoms per spiral. Crystalline sulfur seems to be made of rings, each containing eight sulfur atoms, which fit together to give a normal X-ray pattern.
Most of the sulfur that is produced is used in the manufacture of sulfuric acid (H2SO4). Large amounts of sulfuric acid, nearly 40 million tons, are used each year to make fertilizers, lead-acid batteries, and in many industrial processes. Smaller amounts of sulfur are used to vulcanize natural rubbers, as an insecticide (the Greek poet Homer mentioned "pest-averting sulphur" nearly 2,800 years ago!), in the manufacture of gunpowder and as a dying agent.
In addition to sulfuric acid, sulfur forms other interesting compounds. Hydrogen sulfide (H2S) is a gas that smells like rotten eggs. Sulfur dioxide (SO2), formed by burning sulfur in air, is used as a bleaching agent, solvent, disinfectant and as a refrigerant. When combined with water (H2O), sulfur dioxide forms sulfurous acid (H2SO3), a weak acid that is a major component of acid rain.
Sulfur is a component of black gunpowder, and is used in the vulcanization of natural rubber and a fungicide. It is also used extensively in making phosphatic fertilizers. A tremendous tonnage is used to produce sulfuric acid, the most important manufactured chemical.
It is used to make sulfite paper and other papers, to fumigate, and to bleach dried fruits. The element is a good insulator.
Sulfur is essential to life. It is a minor constituent of fats, body fluids, and skeletal minerals.
Sulfur is found in meteorites. R.W. Wood suggests that the dark area near the crater Aristarchus is a sulfur deposit.
Sulfur occurs native in the vicinity of volcanos and hot springs. It is widely distributed in nature as iron pyrites, galena, sphalerite, cinnabar, stibnite, gypsum, epsom salts, celestite, barite, etc.
Sulfur is commercially recovered from wells sunk into the salt domes along the Gulf Coast of the U.S. Using the Frasch process heated water is forced into the wells to melt the sulfur, which is then brought to the surface.
Sulfur also occurs in natural gas and petroleum crudes and must be removed from these products. Formerly this was done chemically, which wasted the sulfur; new processes now permit recovery. Large amounts of sulfur are being recovered from Alberta gas fields.
Carbon disulfide, hydrogen sulfide, and sulfur dioxide should be handled carefully. Hydrogen sulfide in small concentrations can be metabolized, but in higher concentrations it quickly can cause death by respiratory paralysis.
It quickly deadens the sense of smell. Sulfur dioxide is a dangerous component in atmospheric air pollution.
The stable sulfur isotope-amount ratio n(34S)/n(32S) has been used to distinguish whether animal tissues grew in freshwater or in marine ecosystems. The isotopes do not fractionate (separate) substantially with trophic influences (the movement of sulfur through and into plant and animal systems), and the isotope-amount ratio n(34S)/n(32S) is usually substantially different between freshwater and marine environments. As an example, by analyzing sulfur isotope-amount ratios in bird feathers, the environment in which the bird was living when these feathers developed can be determined. This enables one to track bird habitats and migration patterns throughout the year (Fig. IUPAC.16.1) [141].
Molecules, atoms, and ions of the stable isotopes of sulfur possess slightly different physical and chemical properties, and they commonly will be fractionated during physical, chemical, and biological processes, giving rise to variations in isotopic abundances and in atomic weights. There are substantial variations in the isotopic abundances of sulfur in natural terrestrial materials (Fig. IUPAC.16.2). These variations are useful in investigating the origin of substances and studying environmental, hydrological, and geological processes [13], [17]. The isotope-amount ratio n(34S)/n(32S) can be used to trace natural and anthropogenic sources of sulfur. Examples include studies of acid mine drainage, the cycling of sulfur in agricultural watersheds, groundwater contamination from landfills, and sources of salinity in coastal aquifers [142], [143], [144].
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- Los Alamos National Laboratory, U.S. Department of Energy
- NIST Physical Measurement Laboratory
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